JP2002337789A - Hull vibration reducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hull vibration reducing device capable of reducing vibration generated by the rotation of a stern propeller and attaining energy saving. SOLUTION: This hull vibration reducing device 1 is capable of reducing pressure fluctuation violently acting on the stern bottom 4 by the rotation of a stern propeller 2. The hull vibration reducing device 1 comprises a fin 5 composed of an elastic body and arranged between the stern propeller 2 and the stern bottom 4, directly above the stern propeller 2. The fin 5 absorbs the pressure fluctuation generated by the rotation of the stern propeller 2, with resilience, and the fin is vibrated to perform the operation of a dolphin kick, thus acquiring driving force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus capable of reducing pressure fluctuations acting vigorously on the stern bottom due to rotation of a stern propeller. More specifically, the present invention provides
The present invention relates to a hull vibration reduction device that can reduce pressure fluctuations acting violently on the stern stern bottom and convert the pressure fluctuations into propulsion by providing fins made of an elastic body between the stern propeller and the stern hull. is there.

[0002]

2. Description of the Related Art In general, it is known that in a ship, when a stern propeller rotates, severe pressure fluctuation acts on a stern bottom, and the hull vibrates greatly. this is,
The rotation of the stern propeller causes the fluid near the stern hull to repeat compression / expansion in accordance with the rotation speed of the propeller and the number of propellers.

FIG. 5 is a diagram showing an example of a conventional apparatus for absorbing and reducing the above-mentioned pressure fluctuation. In FIG. 5, the hull vibration reduction device 101 includes a substantially circular rubber film 105 disposed on the bottom 104 of the stern 103 immediately above the stern propeller 102, and water is sealed in the rubber film 105. And a water volume adjusting device 106 capable of adjusting the volume of water inside 105 in accordance with the frequency (Japanese Patent Laid-Open No. 8-188192).

The water volume adjusting device 106 includes a ballast tank 107, a water supply pump 108, an on-off valve 109,
Control valve 110, water supply pipe 111, return pipe 11
And 2. The water supply pipe 111 having the water supply pump 108 and the on-off valve 109 is connected to the ballast tank 1.
07 and the rubber membrane 105 are connected to each other.
8, the water in the ballast tank 107 can be supplied to the rubber film 105. Further, the return pipe 112 provided with the control valve 110 is connected to the rubber film 105 and the ballast tank 1.
07, and the water in the rubber film 105 can be returned to the ballast tank 107 by the operation of the control valve 110.

[0005] The hull vibration reduction apparatus 1 configured as described above.
According to No. 01, the fluctuating pressure by the propeller is
And acts directly on the bottom 104 of the stern 103, and the water volume inside the rubber membrane 105 can be adjusted by the water volume adjusting device 106 in accordance with the frequency so that the fluctuation by the propeller Since the pressure peak is absorbed, generation of impact, vibration, and noise can be prevented.

[0006]

However, according to the conventional hull vibration reducing device described above, it is necessary to provide a rubber film on the stern bottom just above the stern propeller and to provide a water volume adjusting device. , The configuration is complex, and
There is an inconvenience that a large number of components are required and an installation place for the apparatus is required. Further, according to the conventional hull vibration reduction device described above, in order to sufficiently extract the vibration absorption function, maintenance of the device is always required, and there is a disadvantage that labor is required even after installation.

Further, according to the hull vibration reducing device,
In addition to the components and devices, a considerable amount of the fluid to be supplied into the rubber film is required, and the fluid must be replenished. SUMMARY OF THE INVENTION It is an object of the present invention to provide a hull vibration reducing apparatus that solves the above-mentioned disadvantages, reduces vibrations caused by rotation of a stern propeller, and enables energy saving.

[0008]

In order to achieve the above object, a hull vibration damping device according to the first aspect of the present invention is a device capable of reducing pressure fluctuations acting violently on the stern bottom due to rotation of a stern propeller. A fin made of an elastic material is provided between the propeller and the stern hull. Thus, the fins vibrate in response to the pressure fluctuation of the stern propeller directly, and do not directly transmit the pressure fluctuation to the stern, so that the vibration can be reduced. Further, since the fins are simply arranged, the structure is simple, the number of parts is small, the installation area and volume are small, and no maintenance is required. Further, the fins vibrate to act like a dolphin kick, and provide a propulsive force to the ship, thereby achieving an energy saving effect. According to a second aspect of the present invention, in the hull vibration reducing device according to the first aspect, the fin is disposed above a stern propeller, and both ends of the fin on the ship front side are supported by a stern hull. And fixed to the stern hull at predetermined intervals from the stern hull. According to the third aspect of the present invention,
In the hull vibration reduction device described above, the fins are formed in a streamline shape with hard rubber having a cross section that is thicker on a ship front side and gradually thinner toward a ship rear side. According to a fourth aspect of the present invention, in the hull vibration damping device according to the first aspect, the fin has a length in a lateral direction of the vessel at least equal to a rotational diameter of a stern propeller.
5 to 1.5, and the length of the ship in the front-rear direction is formed at least about the thickness of the stern propeller.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 illustrate an embodiment of the present invention. Here, FIG. 1 is a side view for explaining a hull vibration damping device according to an embodiment of the present invention and its operation, FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1, and FIG. FIG. 4 is a cross-sectional view showing a main part of the hull vibration reducing device, and FIG. 4 is a characteristic diagram for explaining the operation of the hull vibration reducing device according to the embodiment of the present invention. Hereinafter, when the directions of the members constituting the present embodiment are described, the bow side is referred to as the front direction, the stern side is referred to as the rear direction, and the direction perpendicular to the front-rear direction is referred to as the lateral direction.

In these figures, a hull vibration reducing device 1 is shown.
Is a device capable of reducing pressure fluctuations acting violently on the stern stern due to the rotation of the stern propeller 2, and is disposed between the stern propeller 2 and the stern hull (bottom) 4 of the stern 3 immediately above the stern propeller 2. The fin 5 includes support members 6, 6 for fixing the front end portions 5 a of the fin 5 to the ship bottom 4 at a predetermined distance H from the ship bottom 4.

The fin 5 has a predetermined area formed of a thin plate made of a material such as hard rubber or a thin metal having a predetermined elasticity. The fins 5 are formed in an asymmetrical shape in longitudinal section between the ship front side and the ship rear side. More specifically, the fins 5
As shown in FIG. 3, the vertical cross section is formed in a streamline shape that is thicker on the front side and gradually thinner toward the rear side. Further, the fin 5 has a length W in a direction (lateral direction) perpendicular to the traveling direction of the marine vessel, which is at least 0.5 to 1.5 of the rotational diameter D of the stern propeller 2 and a length in the longitudinal direction of the marine vessel. The length L is at least 1 to the thickness d of the stern propeller 2.
It is formed about three times. Further, the supports 6, 6
As shown in FIGS. 2 and 3, each of the fins 5 is formed of a thin and rigid metal plate, and the front end portions 5a of the fins 5 are fixed at a distance H from the bottom 4 of the stern 3. It is a member to do.

The hull vibration reducing device 1 constructed as described above.
1 will be described with reference to FIGS. In FIG. 4, the horizontal axis represents the frequency of pressure fluctuation (rotational speed (rpm) of the stern propeller 2 × the number of blades), and the horizontal axis represents the propulsion force of the fins 5. When the stern propeller 2 rotates, when the wings of the stern propeller 2 approach the bottom 4, the stern propeller 2 receives water pressure (pressure). When the wings move away from the bottom 4, the wing receives the opposite pressure, and pressure fluctuation is applied to the bottom 4. Has already been described. The frequency of the pressure fluctuation is proportional to the rotation speed when the propeller shaft makes one rotation and the number of blades of the stern propeller 2.

The pressure from the stern propeller 2 is as follows.
The fins 5 disposed directly above the stern propeller 2 receive directly. Since the fins 5 are made of an elastic material such as hard rubber, as shown in FIG. 1, they operate so as to vibrate up and down according to the pressure and absorb the pressure. As a result, the pressure fluctuation from the stern propeller 2 is not directly transmitted to the bottom 4 of the stern 3, so that the vibration caused by the pressure fluctuation due to the rotation of the stern propeller 2 can be reduced.

The fins 5 vibrate up and down in response to pressure fluctuations caused by the rotation of the stern propeller 2 as shown by the arrows in FIG. 1 and act like a dolphin kick to apply a propulsive force to the ship. Become. At this time, the propulsion force generated by the vibration of the fins 5 increases when the frequency of the pressure fluctuation (surface force) matches the natural frequency fc of the fins 5, as can be seen from FIG.
It is specified that the frequency decreases sharply as the frequency fc increases. As described above, according to the hull vibration reduction device 1 according to the present embodiment, the fin 5 is located immediately above the stern propeller 2 and between the stern propeller 2 and the stern 3.
, The structure is extremely simple, the number of parts is extremely small, and the installation cost can be reduced.

Further, since the hull vibration damping device 1 has no parts other than the fins 5 and the support 6, the installation area and volume are small, and no special maintenance is required. Further, the fin 5 is vibrated by a surface force that does not originally generate a propulsive force to cause the fin 5 to act like a dolphin kick, thereby providing a propulsive force to the ship, thereby saving energy.

[0016]

EXAMPLE Here, concrete experimental results are shown. The surface force of the actual ship is, for example, 400 [Kg / square meter], and the Dp of the stern propeller 2 under pressure.
(Diameter) = Area equivalent to 6m propeller [square meter]
Then, the pressure applied to the area becomes 400 × 30 = 12000 [Kg] = 12 [tons]. The fins 5 made of an elastic body receive a part of the pressure applied to the area, thereby reducing the pressure fluctuation applied to the ship bottom 4. Further, assuming that the propulsion force of the entire ship is about 100 [ton] and the propulsion force generated by the vibration of the fins 5 is 0.5 [percent] of the entire ship, 0.5 [ton] Becomes Therefore, the ratio of surface force to propulsion is 24: 1.

[0017]

As described above, according to the hull vibration reducing apparatus according to the first aspect of the present invention, since the fin composed of an elastic body is provided between the stern propeller and the stern hull, the stern propeller has Vibration due to rotation can be reduced. Further, according to the hull vibration reduction device, the fins vibrate due to pressure fluctuations caused by the rotation of the stern propeller to act as a dolphin kick, thereby generating a propulsion force and conserving energy.

[Brief description of the drawings]

FIG. 1 is a side view illustrating a hull vibration reduction device according to an embodiment of the present invention and its operation.

FIG. 2 is a side view showing the hull vibration reduction device according to the embodiment of the present invention, and is a cross-sectional view taken along line AA of FIG.

FIG. 3 is a cross-sectional view showing a main part of the hull vibration reduction device according to the embodiment of the present invention.

FIG. 4 is a characteristic diagram for explaining a relationship between a propulsion force and a frequency of pressure fluctuation of the hull vibration reduction device according to the embodiment of the present invention.

FIG. 5 is a diagram showing an example of a conventional device for absorbing and reducing pressure fluctuations.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hull vibration reduction device 2 Stern propeller 3 Stern 4 Ship bottom 5 Fin 5a Front both ends 6 Support

Claims (4)

[Claims] 1. A hull vibration reducing device, comprising: a fin made of an elastic body provided between a stern propeller and a stern hull in a device capable of reducing pressure fluctuations acting violently on a stern hull due to rotation of a stern propeller. . 2. The stern hull according to claim 2, wherein the fin is disposed above a stern propeller, and both ends of the fin on the stern hull are fixed to the stern hull by support members at predetermined intervals. The hull vibration reduction device according to claim 1, wherein: 3. The hull vibration damping device according to claim 2, wherein the fins are formed of hard rubber in a streamline shape having a cross section that is thicker on a ship front side and gradually thinner toward a ship rear side. 4. The fin is formed such that the length in the lateral direction of the marine vessel is at least 0.5 to 1.5 times the rotational diameter of the stern propeller, and the length in the longitudinal direction of the marine vessel is at least about the thickness of the stern propeller. The hull vibration reduction device according to claim 1, wherein: